1. Field of Invention
This invention relates to utilizing a knowledge-based system to ensure network radiality during reconfiguration of a radial power distribution system.
2. Description of Prior Art
Previous methods for distribution system reconfiguration employed one of three possible techniques to ensure that network radiality is preserved:    1. Constraints are included that ensure a bus's supply is equal to its demand.    2. The product of power flows for line sections about a loop is equal to 0. Also, the product of binary variables representing switch status, such that 1 is closed and 0 is open, for line sections about a loop is equal to 0.    3. A branch exchange is performed. Closing one line section results in the opening of another.
The first two methods can only be implemented with numerical methods. It is necessary to ensure that the supply and demand of each bus is equal, but solution through this technique is inefficient when employed in conjunction with a knowledge-based method. It would be necessary to calculate a power flow equation including losses for every bus in the network each time a switching operation is examined. Therefore, it is somewhat impractical to implement these techniques.
The third method, which involves a branch exchange, can be somewhat inefficient in terms of solution time during optimization of power distribution system operations if not initialized by a good starting point, but can be employed in knowledge-based methods. Roytelman et al proposed a simple formulation that assumes all line sections are equipped with a tie or sectionalizer. Their algorithm only determines which neighbor to open next if a previously open switch is closed. Other previously proposed methods assume all line sections are equipped with a switch; this is an oversimplification of the reconfiguration problem. Loosely incorporating the work of Roytelman et al, the knowledge-based system improves the branch exchange method previously applied to the reconfiguration problem. Line sections equipped with a switch are recognized and a required switch closing, associated with a switch opening, is found or a required switch opening, associated with a switch closing, is found. Radiality is ensured, even though the system is initially represented as a meshed network.
3. Objects and Advantages
Accordingly besides the objects and advantages described in this patent, some objects and advantages of the matrix-structured knowledge-based system for network radiality are                The intelligent system is implemented with knowledge-based methods and without numerical methods. This reduces solution time, which is important due to time constraints in distribution system reconfiguration.        The intelligent system does not assume that all line sections are equipped with a tie or sectionalizer.        The intelligent system does not assume that all line sections are equipped with a switch. The line section table keeps track of which line sections are equipped with a switch and whether there is an open or closed switch on that line section.        The intelligent system does not assume all line sections are the same. The line section table keeps track of whether a line section is a source, terminal, or intermediate node. This affects switching decisions because the intelligent system should not isolate a terminal node or not use all sources to supply the network.        The intelligent system finds an initially open switch to close to assume the load transfer necessitated by a switch opening. Alternatively, the intelligent system finds an initially closed switch to open because of the load transfer necessitated by a switch closing.        The intelligent system does a breadth first search in finding a switch to open because this increases the likelihood of finding a corresponding switch to open in greater proximity of the switch being closed. Alternatively, the intelligent system does a breadth first search in finding a switch to close because this increases the likelihood of finding a corresponding switch to close in greater proximity of the switch being opened.        The intelligent system checks that all buses of the subsystem are supplied.        The intelligent system checks for the formation of isolated loops.        The intelligent system for network radiality can be used during distribution system reconfiguration immediately after failure of power system components, during system optimization procedures, during network maintenance, and after power outages.        The intelligent system enhances network reliability and can prevent power outages, which cost individuals and organizations tremendous productivity, time, and money.        
Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings.